free
Explanation
This comic plays on the well-known tech industry adage: "If the service is free, you are the product" -- meaning that free services (like social media platforms) monetize users' data and attention rather than charging them directly.
In the first panel, a man walks past a shop advertising "Today: Free Sandwiches!" and looks visibly disturbed. In the flashback panel labeled "Earlier," we see a disheveled, conspiracy-minded figure warning him: "One thing you gotta know about this world, man. If the service is free, you are the product."
The humor comes from the man applying this tech-industry wisdom far too literally and broadly. He's now terrified of a shop giving away free sandwiches, apparently believing that accepting a free sandwich means he will somehow become "the product." The comic satirizes how internet-savvy aphorisms, while often valid in their original context, can become absurd when treated as universal laws and applied to every situation -- sometimes a free sandwich is just a free sandwich.